SS‐OFDM: an enhanced multicarrier transmission scheme based on variable granularity spectrum allocation for 5G

Abstract

When oriented to the needs of the future fifth generation (5G) networks, orthogonal frequency division multiplexing (OFDM), as a modulation scheme, has some drawbacks: high out-of-band emission (OOBE) of power, relatively low spectrum efficiency, and poor flexibility for allocating resources. In this study, a subband superposed OFDM (OFDM) scheme, based on a variable granularity spectrum allocation, is proposed to divide the transmission channel into several subbands considering the compromises between single-carrier and multicarrier spectrum utilisation. For accommodating the diverse 5G scenarios, appropriate signalling parameters can be independently configured among the subbands. A multistage polyphase interpolator is developed in the transmitter to reduce the implementation cost of time-domain filter depressing the OOBE. Extremely narrow frequency guard intervals between subbands are realised by filtering to maximise the spectrum utilisation. At the receiver, a subband decision feedback and feedforward equaliser, relying on the subband's oversampling architecture, is designed to utilise the diversity gains in both the Doppler and the multipath delay domains. Simulation results indicate that the spectral efficiency, in terms of the spectrum utilisation rate, is increased up to 98.5 % and that the bit-error-rate performance is significantly improved for the subbands experiencing high-speed mobile channels while preserving a relatively low computational complexity.